Transistor



March 18, 1958 P. J.- W. JOCHEMS TRANSISTOR Filed April 19, 1954 lN VENTOR PIETER JOHANNES WILHE LMUS JOCH EMS AGENT United States Patent 3 FTRANSISTOR Pieter Johannes Wiihelmus Jochems, Eindhoven, Netherlands,assignor, by mesne assignments, to North American Philips Company, Inc.,New York, N. Y., a corporation of Delaware Application April 19, 1954,Serial No. 424,173

Claims priority, application Netherlands May 1, 1953 12 Claims. (Cl.317-235) This invention releates to transistors comprising asemiconductive member having secured to it one base and at least twoother electrodes, that is to say at least one emitter and one collector.Barrier layers or rectifying junctions are provided between the memberand the emitter or collector terminals, but in general, such a barrieris not provided between the member and the base. Said member is usuallya monocrystal.

It is known that, when an emitter and a base are provided in an electriccircuit, a variation of the current I in this circuit involves avariation of the current I in a second circuit including the base and acollector.

At a constant voltage E in the collector circuit, the ratio of saidvariations is the current amplification factor This factor shouldpreferably be as large as possible.

The invention has inter alia for its object to increase the currentamplification factor, particularly at high values of 1 and 1,. It isbased on the recognition that under given conditions a considerable partof the current supplied by the emitter may flow to the base and does notcontribute to influencing the collector current. The invention providesmeans for considerably reducing said loss.

Furthermore, the invention permits of reducing the so-called saturationcurrent in the collector circuit, that is to say the collector currentat an emitter current equal to zero and at a constant collector voltage.

According to the invention, the semi-conductive member comprises atleast one insulating part whereof the surface at least partly adjoins anemitter or a collector. That is, a nonconductive region is interposedbetween the emitter or collector and the base electrode.

Consequently, such an insulating part compels the current to follow agiven direction and diminishes the ineffective part of said emitter orcollector.

Such an insulating part preferably consists of a cavity in thesemi-conductive member, for example a bore or a sawcut.

The emitter and collector, or plural emitters and collectors, as thecase may be, are preferably of the diffusion type, which may, forexample, be obtained by fusing given metals onto the semi-conductivemember. As a matter of fact, such emitters and collectors, which have acomparatively large surface, and which are sometimes referred to asbroad area rectifying connections, frequently possess parts which do notcontribute to the chiciency of the transistor.

The invention is of particular importance for transistors ofcomparatively high power, whose emitter and collector have a largesurface and are alternately juxtaposed on the semi-conductive member.

In order that the invention may be readily carried into effect, it willnow be described in greater detail with 2,827,599 Patented Mar. 18, 1958reference to the accompanying drawing, which represents several examplesthereof and in which Fig. 1 is a sectional view of a transistorcomprising one emitter and one collector.

Fig. 2 is a sectional view of a transistor comprising a number of suchemitters and collectors.

Figures 3 and 5 are perspective views of a semi-conductive member andFigures 4, 4a, 6 and 7 are sectional views of transistors made by meansof said member.

The transistor shown in Fig. 1 comprises a semi-conductive member orbody 1, for example consisting of a mono-crystal of n-type germanium,which is soldered to a base 2, which thus constitutes a base ohmicconnection to the body 1. This member 1 has secured to it an emitter 3and a collector 4, both of which may consist of a quantity of indiumfused onto the body. in this manner the underlying germanium is locallyconverted into p-type germanium at the two regions indicated byreference numeral 5, as indicated by double cross-hatching, barriers orrectifying junctions being situated at the limiting surfaces of theseopposite types of germanium. An insulating part or non-conductive regionin the form of a cavity 6 is situated beneath the emitter 3 and thusbetween the latter and the adjacent ptype region 5, and the baseconnection 2. Thus a part '7 of the surface of the emitter 3 is madeinactive with the effect that the remaining active surface influencesthe collector 4 to a relatively higher degree. However, a part of thecontact surface of the emitter 3 and the semi-conductive member 1, whichpart is situated at the left of the cavity 6, still provides emittercurrent which does not practically affect the collector.

Therefore it is advisable to provide insulating parts beneath an emittersituated between two collectors. Fig. 2 shows a transistor comprisingtwo emitters 3 and three collectors 4. Beneath each emitter and eachcollector are provided cavities 6 so that all surface parts of theemitters, which contact with the semi-conductive member, face acollector, and the current passing through the emitters (to be connectedin parallel) is able to exert a comparatively strong influence on thecurrent passing through the collectors (also to be connected inparallel). Furthermore, the active surfaces of the collectors mainlyface the emitters, thus avoiding as much as possible a direct currentpath from the collectors to the base and reducing the saturation currentof the collector.

The shape of the insulating or non-conductive parts will partly dependupon the properties of the semi-conductive material. When this materialis germanium it may, for example, be processed by sawing or drilling.

A number of parallel slots 3, as shown in Fig. 3, may be provided bysawing in the surface of the semi-conductive member remote from thebase. The upper part of said slots is filled with longitudinal indiumstrips 9. Upon heating, this indium metal will fuse together with thegermanium and partly difiuse into it to produce the regions of oppositeconductivity type to that of the member 1 (Fig. 4). In order to preventthe indium from filling the slots completely, the bottom of said slotsmay be covered with insulating material 14, for example SiO as shown inFig. 4a.

Figures 5 to 7 show another embodiment in which openings 11 are drilledin a fiat semi-conductive member 10 (Fig. 5). Said openings may eitherextend to the base 2, as shown in Fig. 6 or through said base as shownin Fig. 7. Into each opening a drop of indium is melted, which drops maybe alternately connected as emitter and collector respectively.

If the transistor is required to be etched after melting on the emittersand the collectors, preferred constructions comprise insulating parts inthe form of cavities which extend to the outer surface of the member asshown in Fig. 7 and consequently not those shown in Fig. 6. In thefirst-mentionedcase, the etching liquid is allowedto pene' trate intothe cavities.

What is claimed is:

l, A transistor comprising a semi-conductive member of one conductivitytype, a base ohmic connection to said member, a pair of spaced regionsin said member of the opposite conductivity type, and emitter-andcollector terminal connections to said regions, said member containinganon-conductive region located between at least one ,of said regions ofthe opposite conductivity type and said of one conductivity type, a baseohmic connection to one 3 surface of said member, and a plurality ofbroad area rectifying connections to another surface of said member,said member containing at least one non-conducting portion disposedunderneath one of said broad area rectifying connections and between thelatter and the base connection. 7 a

' 7. A transistor as set forth in claim 6 wherein a no conductingportion is present underneath each ,of the broad area rectifyingconnections. 7 V V Y r V 8. A transistor comprising a semi-conductivemember of one conductivity type, a base ohmic connection to one surfaceof said member, and at least three broad area rec-'- tifying connectionsto another surface of said member, said member containing at least onenon-conducting por 7 tion disposed underneath one of said broad ar arectifying connections and between the latter and the base connec- 'oneelectrode.

4' i tion, the remaining two rectifying connections being electricallyinterconnected and being situated on opposite sides of said onerectifying'connection,

9. A transistor as set forth 'in claim 8, wherein the rectifyingconnections have an elongated form and extend approximately parallel, toone, another. V

10. A transistor comprising a semi-conductive body having ;a groove ofgiven width in one surface thereof defining anon-conducting portion insaid body, emitter and collector electrodes connected in spacedrelationship 7 to said body, at least one of said electrodes beingconstituted-by a metallic body having a width greater than.

said given width" disposed over said groove in contact With andxliffusedinto adjacent surfaces thereof, the bottom of said groove remaining freeof conductive material, and a base electrode secured toca surface ofsaid semi-conductive body opposite said one'surface.

ll. A transistor comprising a' semi-conductive body having a cylindricalbore of given diameter extending through said body and defining in saidbody a non-conducting portion, emitter and collector electrodes connected in spaced relationship to said body, one of said electrodes beingconstitutedby a metallic body having at least one dimension greater thansaid given diameter and disposed over one end of said bore in contactWith'and difiu'sed into surface portions of said body surrounding saidbore, the bottom of said bore remaining free of con ductive material,and a base electrode secured to a sur-P face of 'said'semi-conductivebody opposite from said 12. A transistor as set forth claim 11 whereinbase electrode has an opening therein aligned with said cylindricalbore. 7

References Cited in the file of this patent 7 UNITED STATES PATENTSShockley *Jan. 19, 1 954 7

1. A TRANSISTOR COMPRISING A SEMI-CONDUCTIVE MEMBER OF ONE CONDUCTIVITYTYPE, A BASE OHMIC CONNECTION TO SAID MEMBER, A PAIR OF SPACED REGIONSIN SAID MEMBER OF THE OPPOSITE CONDUCTIVITY TYPE, AND EMITTER ANDCOLLECTOR TERMINAL CONNECTIONS TO SAID REGIONS, SAID MEMBER CONTAIN-